1. Field of the Invention
The present invention is for a slotted spool valve for use in a speed control apparatus.
2. Description of the Prior Art
The prior art speed control apparatus disclosed in U.S. Pat. No. 3,703,810 includes an arrangement of gears and other components which operates a rotary spool valve 22 in a manifold 17 in which the rotary spool valve 22 resides. Variation from the desired controlled speed as sensed or determined by an input shaft 14, such as caused by imposing a load on the hydraulic motor 10 referred to in said patent 3,703,810, for example, would cause rotation of the rotary spool valve 22 to decrease the amount of pressurized hydraulic fluid bypassed in the manifold 17, thereby allowing increased porting of pressurized hydraulic fluid to the motor 10 and thereby compensating for the speed of the motor, such compensation being of lasting duration or being only momentarily. Upon regaining and coming up to speed, or even when slightly overspeeding, such rotation speed is yet sensed by the input shaft 14, and the rotary spool valve 22 is rotatingly positioned in the opposite direction to establish or limit the revolutions per minute of the motor 10 by increasing the amount of pressurized hydraulic fluid bypassed, thereby decreasing the amount of ported pressurized hydraulic fluid to the motor 10. Such controlling or governing of motor speed at higher RPMs of the motor 10 virtually goes unnoticed to an observer as the compensations occur over fractions of a second. However, during desired lower RPM operation of the motor 10, undesirable speed variations become noticeable to an observer where speed variations, being sometimes referred to as cogging, are manifested when pressurized hydraulic fluid is delivered to the motor in a lagging or sluggish fashion. The relationship of the rotary spool valve 22 angular rotation to the amount of fluid at the motor 10 is such that the amount of fluid bypassed or not bypassed in a condition requiring compensation is not suitable to prevent noticeable cogging. The ports 24 which determine the amount of bypassing are circular in shape and as such do not provide for sufficiently decreased bypassing to allow for increased amounts of pressurized hydraulic fluid to be bypassed or delivered in a timely fashion to the motor 10 during low speed operation. Insufficiently pressurized hydraulic control fluid bypass or delivery allows the motor to laggingly slow and then to laggingly come up to speed (or approach overspeed) to cause cogging. Clearly, what is needed is a restructuring of the ports or orifices of a rotary spool valve to allow for bypass control to deliver and control sufficient quantities and pressure of pressurized hydraulic fluid in a timely fashion to prevent hydraulic motor speed variations and to stabilize rotation at low motor speeds.
The general purpose of the present invention is to provide a slotted spool valve for use in a speed control apparatus.
According to one embodiment of the present invention, there is provided a slotted spool valve the major components of which are a liner and a spool which is accommodated by the liner. The slotted spool valve can be incorporated into existing manifolds or can be incorporated into newly manufactured manifolds. The cylindrical liner is fabricated to be accommodated by a bore extending into or through a manifold and is sealingly fitted therein with a plurality of O-ring seals. Pressurized hydraulic fluid is delivered through the manifold to provide pressurized hydraulic fluid to a motor and to the slotted spool valve which can control motor speed by varyingly bypassing pressurized hydraulic fluid around the motor. A plurality of liner supply ports around and about the liner of the slotted spool valve communicate with and supply pressurized hydraulic fluid to one or more spool supply ports positioned on the spool of the slotted spool valve. The pressurized hydraulic fluid passes through the spool supply ports and through the interior of the spool to exit the spool at a plurality of rectangular-shaped spool bypass ports located around and about one end of the spool which communicate with a plurality of rectangular-shaped liner bypass ports located around and about the encompassing liner. Full communication of pressurized hydraulic fluid between the fully aligned rectangular-shaped spool bypass ports and the rectangular-shaped liner bypass ports results in bypassing the pressurized hydraulic fluid around the motor to cease or slow motor operation. Rotation of the spool toward lesser alignment of the rectangular-shaped spool bypass ports and the rectangular-shaped liner bypass ports results in reducing the bypassing, whereby the motor receives an increased share of pressurized hydraulic fluid to increase the motor speed. The relationship of the rectangular-shaped spool bypass ports and the rectangular-shaped liner bypass ports when compared to the relationship of round-shaped spool bypass ports and round-shaped liner bypass ports is such that only a small angular rotation of the spool in the slotted spool valve as rotationally positioned by an actuation shaft is required to produce the same degree of bypassing (or fluid delivery) as that produced by a valve having round bypassing ports and requiring a comparatively larger angular rotation by an actuation shaft of the spool having round liner or spool bypass ports. Or, for the same amount of actuation shaft rotation, a more rapid response is provided by the slotted spool valve where a proportionately larger passageway is provided due to the cross-section of the geometry provided therein. As such, response time of the motor is improved as pressurized hydraulic fluid is either bypassed about the motor or delivered to the motor in a more rapid fashion due to the increased sensitivity and shortened response time of the slotted spool valve incorporating rectangular-shaped spool bypass ports and rectangular-shaped liner bypass ports.
One significant aspect and feature of the present invention is the use of a slotted spool valve to control bypassing, metering or supply of hydraulic fluid to a hydraulic motor.
Another significant aspect and feature of the present invention is a slotted spool valve having a spool with rectangular ports and a liner with rectangular ports which are positioned with respect to each other to rapidly control the bypassing, metering of and supply of pressurized hydraulic fluid to a hydraulic motor.
Still another significant aspect and feature of the present invention is the use of a slotted spool valve incorporating rectangular ports to significantly increase responsiveness and sensitivity of a spool valve to increase the responsiveness of a hydraulic motor at low speeds.
Yet another significant aspect and feature of the present invention is the increased responsiveness and sensitivity of spool valves having rectangular-shaped spool and liner bypass ports over spool valves having round-shaped spool and liner bypass ports.
Another significant aspect and feature of the present invention is a slotted spool valve having a spool which can be rotatably positioned.
Having thus briefly described an embodiment of the present invention, it is the principal object of the present invention to provide a slotted spool valve having increased response and sensitivity for use in a speed control apparatus.